/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2009, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at http://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * $Id: content_encoding.c,v 1.31 2009-02-17 12:14:52 bagder Exp $
 ***************************************************************************/

#include "setup.h"

#ifdef HAVE_LIBZ

#include <stdlib.h>
#include <string.h>

#include "urldata.h"
#include <api/libcurl/curl.h>
#include "sendf.h"
#include "content_encoding.h"
#include "memory.h"

#include "memdebug.h"

/* Comment this out if zlib is always going to be at least ver. 1.2.0.4
   (doing so will reduce code size slightly). */
#define OLD_ZLIB_SUPPORT 1

#define DSIZ 0x10000             /* buffer size for decompressed data */

#define GZIP_MAGIC_0 0x1f
#define GZIP_MAGIC_1 0x8b

/* gzip flag byte */
#define ASCII_FLAG   0x01 /* bit 0 set: file probably ascii text */
#define HEAD_CRC     0x02 /* bit 1 set: header CRC present */
#define EXTRA_FIELD  0x04 /* bit 2 set: extra field present */
#define ORIG_NAME    0x08 /* bit 3 set: original file name present */
#define COMMENT      0x10 /* bit 4 set: file comment present */
#define RESERVED     0xE0 /* bits 5..7: reserved */

static CURLcode
process_zlib_error(struct connectdata *conn, z_stream *z)
{
	struct SessionHandle *data = conn->data;
	if (z->msg)
		failf (data, "Error while processing content unencoding: %s",
			   z->msg);
	else
		failf (data, "Error while processing content unencoding: "
			   "Unknown failure within decompression software.");

	return CURLE_BAD_CONTENT_ENCODING;
}

static CURLcode
exit_zlib(z_stream *z, zlibInitState *zlib_init, CURLcode result)
{
	inflateEnd(z);
	*zlib_init = ZLIB_UNINIT;
	return result;
}

static CURLcode
inflate_stream(struct connectdata *conn,
			   struct SingleRequest *k)
{
	int allow_restart = 1;
	z_stream *z = &k->z;          /* zlib state structure */
	uInt nread = z->avail_in;
	Bytef *orig_in = z->next_in;
	int status;                   /* zlib status */
	CURLcode result = CURLE_OK;   /* Curl_client_write status */
	char *decomp;                 /* Put the decompressed data here. */

	/* Dynamically allocate a buffer for decompression because it's uncommonly
	   large to hold on the stack */
	decomp = malloc(DSIZ);
	if (decomp == NULL)
	{
		return exit_zlib(z, &k->zlib_init, CURLE_OUT_OF_MEMORY);
	}

	/* because the buffer size is fixed, iteratively decompress and transfer to
	   the client via client_write. */
	for (;;)
	{
		/* (re)set buffer for decompressed output for every iteration */
		z->next_out = (Bytef *)decomp;
		z->avail_out = DSIZ;

		status = inflate(z, Z_SYNC_FLUSH);
		if (status == Z_OK || status == Z_STREAM_END)
		{
			allow_restart = 0;
			if (DSIZ - z->avail_out)
			{
				result = Curl_client_write(conn, CLIENTWRITE_BODY, decomp,
										   DSIZ - z->avail_out);
				/* if !CURLE_OK, clean up, return */
				if (result)
				{
					free(decomp);
					return exit_zlib(z, &k->zlib_init, result);
				}
			}

			/* Done? clean up, return */
			if (status == Z_STREAM_END)
			{
				free(decomp);
				if (inflateEnd(z) == Z_OK)
					return exit_zlib(z, &k->zlib_init, result);
				else
					return exit_zlib(z, &k->zlib_init, process_zlib_error(conn, z));
			}

			/* Done with these bytes, exit */
			if (status == Z_OK && z->avail_in == 0)
			{
				free(decomp);
				return result;
			}
		}
		else if (allow_restart && status == Z_DATA_ERROR)
		{
			/* some servers seem to not generate zlib headers, so this is an attempt
			   to fix and continue anyway */

			(void) inflateEnd(z);     /* don't care about the return code */
			if (inflateInit2(z, -MAX_WBITS) != Z_OK)
			{
				free(decomp);
				return exit_zlib(z, &k->zlib_init, process_zlib_error(conn, z));
			}
			z->next_in = orig_in;
			z->avail_in = nread;
			allow_restart = 0;
			continue;
		}
		else                        /* Error; exit loop, handle below */
		{
			free(decomp);
			return exit_zlib(z, &k->zlib_init, process_zlib_error(conn, z));
		}
	}
	/* Will never get here */
}

CURLcode
Curl_unencode_deflate_write(struct connectdata *conn,
							struct SingleRequest *k,
							ssize_t nread)
{
	z_stream *z = &k->z;          /* zlib state structure */

	/* Initialize zlib? */
	if (k->zlib_init == ZLIB_UNINIT)
	{
		z->zalloc = (alloc_func)Z_NULL;
		z->zfree = (free_func)Z_NULL;
		z->opaque = 0;
		z->next_in = NULL;
		z->avail_in = 0;
		if (inflateInit(z) != Z_OK)
			return process_zlib_error(conn, z);
		k->zlib_init = ZLIB_INIT;
	}

	/* Set the compressed input when this function is called */
	z->next_in = (Bytef *)k->str;
	z->avail_in = (uInt)nread;

	/* Now uncompress the data */
	return inflate_stream(conn, k);
}

#ifdef OLD_ZLIB_SUPPORT
/* Skip over the gzip header */
static enum
{
	GZIP_OK,
	GZIP_BAD,
	GZIP_UNDERFLOW
} check_gzip_header(unsigned char const *data, ssize_t len, ssize_t *headerlen)
{
	int method, flags;
	const ssize_t totallen = len;

	/* The shortest header is 10 bytes */
	if (len < 10)
		return GZIP_UNDERFLOW;

	if ((data[0] != GZIP_MAGIC_0) || (data[1] != GZIP_MAGIC_1))
		return GZIP_BAD;

	method = data[2];
	flags = data[3];

	if (method != Z_DEFLATED || (flags & RESERVED) != 0)
	{
		/* Can't handle this compression method or unknown flag */
		return GZIP_BAD;
	}

	/* Skip over time, xflags, OS code and all previous bytes */
	len -= 10;
	data += 10;

	if (flags & EXTRA_FIELD)
	{
		ssize_t extra_len;

		if (len < 2)
			return GZIP_UNDERFLOW;

		extra_len = (data[1] << 8) | data[0];

		if (len < (extra_len + 2))
			return GZIP_UNDERFLOW;

		len -= (extra_len + 2);
		data += (extra_len + 2);
	}

	if (flags & ORIG_NAME)
	{
		/* Skip over NUL-terminated file name */
		while (len && *data)
		{
			--len;
			++data;
		}
		if (!len || *data)
			return GZIP_UNDERFLOW;

		/* Skip over the NUL */
		--len;
		++data;
	}

	if (flags & COMMENT)
	{
		/* Skip over NUL-terminated comment */
		while (len && *data)
		{
			--len;
			++data;
		}
		if (!len || *data)
			return GZIP_UNDERFLOW;

		/* Skip over the NUL */
		--len;
		++data;
	}

	if (flags & HEAD_CRC)
	{
		if (len < 2)
			return GZIP_UNDERFLOW;

		len -= 2;
		data += 2;
	}

	*headerlen = totallen - len;
	return GZIP_OK;
}
#endif

CURLcode
Curl_unencode_gzip_write(struct connectdata *conn,
						 struct SingleRequest *k,
						 ssize_t nread)
{
	z_stream *z = &k->z;          /* zlib state structure */

	/* Initialize zlib? */
	if (k->zlib_init == ZLIB_UNINIT)
	{
		z->zalloc = (alloc_func)Z_NULL;
		z->zfree = (free_func)Z_NULL;
		z->opaque = 0;
		z->next_in = NULL;
		z->avail_in = 0;

		if (strcmp(zlibVersion(), "1.2.0.4") >= 0)
		{
			/* zlib ver. >= 1.2.0.4 supports transparent gzip decompressing */
			if (inflateInit2(z, MAX_WBITS + 32) != Z_OK)
			{
				return process_zlib_error(conn, z);
			}
			k->zlib_init = ZLIB_INIT_GZIP; /* Transparent gzip decompress state */

		}
		else
		{
			/* we must parse the gzip header ourselves */
			if (inflateInit2(z, -MAX_WBITS) != Z_OK)
			{
				return process_zlib_error(conn, z);
			}
			k->zlib_init = ZLIB_INIT;   /* Initial call state */
		}
	}

	if (k->zlib_init == ZLIB_INIT_GZIP)
	{
		/* Let zlib handle the gzip decompression entirely */
		z->next_in = (Bytef *)k->str;
		z->avail_in = (uInt)nread;
		/* Now uncompress the data */
		return inflate_stream(conn, k);
	}

#ifndef OLD_ZLIB_SUPPORT
	/* Support for old zlib versions is compiled away and we are running with
	   an old version, so return an error. */
	return exit_zlib(z, &k->zlib_init, CURLE_FUNCTION_NOT_FOUND);

#else
	/* This next mess is to get around the potential case where there isn't
	 * enough data passed in to skip over the gzip header.  If that happens, we
	 * malloc a block and copy what we have then wait for the next call.  If
	 * there still isn't enough (this is definitely a worst-case scenario), we
	 * make the block bigger, copy the next part in and keep waiting.
	 *
	 * This is only required with zlib versions < 1.2.0.4 as newer versions
	 * can handle the gzip header themselves.
	 */

	switch (k->zlib_init)
	{
		/* Skip over gzip header? */
	case ZLIB_INIT:
	{
		/* Initial call state */
		ssize_t hlen;

		switch (check_gzip_header((unsigned char *)k->str, nread, &hlen))
		{
		case GZIP_OK:
			z->next_in = (Bytef *)k->str + hlen;
			z->avail_in = (uInt)(nread - hlen);
			k->zlib_init = ZLIB_GZIP_INFLATING; /* Inflating stream state */
			break;

		case GZIP_UNDERFLOW:
			/* We need more data so we can find the end of the gzip header.  It's
			 * possible that the memory block we malloc here will never be freed if
			 * the transfer abruptly aborts after this point.  Since it's unlikely
			 * that circumstances will be right for this code path to be followed in
			 * the first place, and it's even more unlikely for a transfer to fail
			 * immediately afterwards, it should seldom be a problem.
			 */
			z->avail_in = (uInt)nread;
			z->next_in = malloc(z->avail_in);
			if (z->next_in == NULL)
			{
				return exit_zlib(z, &k->zlib_init, CURLE_OUT_OF_MEMORY);
			}
			MEMCPY(z->next_in, k->str, z->avail_in);
			k->zlib_init = ZLIB_GZIP_HEADER;   /* Need more gzip header data state */
			/* We don't have any data to inflate yet */
			return CURLE_OK;

		case GZIP_BAD:
		default:
			return exit_zlib(z, &k->zlib_init, process_zlib_error(conn, z));
		}

	}
	break;

	case ZLIB_GZIP_HEADER:
	{
		/* Need more gzip header data state */
		ssize_t hlen;
		unsigned char *oldblock = z->next_in;

		z->avail_in += nread;
		z->next_in = realloc(z->next_in, z->avail_in);
		if (z->next_in == NULL)
		{
			free(oldblock);
			return exit_zlib(z, &k->zlib_init, CURLE_OUT_OF_MEMORY);
		}
		/* Append the new block of data to the previous one */
		MEMCPY(z->next_in + z->avail_in - nread, k->str, nread);

		switch (check_gzip_header(z->next_in, z->avail_in, &hlen))
		{
		case GZIP_OK:
			/* This is the zlib stream data */
			free(z->next_in);
			/* Don't point into the malloced block since we just freed it */
			z->next_in = (Bytef *)k->str + hlen + nread - z->avail_in;
			z->avail_in = (uInt)(z->avail_in - hlen);
			k->zlib_init = ZLIB_GZIP_INFLATING;   /* Inflating stream state */
			break;

		case GZIP_UNDERFLOW:
			/* We still don't have any data to inflate! */
			return CURLE_OK;

		case GZIP_BAD:
		default:
			free(z->next_in);
			return exit_zlib(z, &k->zlib_init, process_zlib_error(conn, z));
		}

	}
	break;

	case ZLIB_GZIP_INFLATING:
	default:
		/* Inflating stream state */
		z->next_in = (Bytef *)k->str;
		z->avail_in = (uInt)nread;
		break;
	}

	if (z->avail_in == 0)
	{
		/* We don't have any data to inflate; wait until next time */
		return CURLE_OK;
	}

	/* We've parsed the header, now uncompress the data */
	return inflate_stream(conn, k);
#endif
}
#endif /* HAVE_LIBZ */
